Flashbacks and HPPD: A Clinical-oriented Concise Review

A unique characteristic of LSD, LSD-like and substances with hallucinogenic properties is the recurrence of some or all the hallucinogenic symptoms which had appeared during the intoxication after the immediate effects of the substance had worn off. This recurring syndrome, mainly visual, is not clearly understood. The terms Flashback and Hallucinogen Persisting Perception Disorder (HPPD) have been used interchangeably in the professional literature. We have observed at least two different recurrent syndromes, the first Flashback Type we refer to as HPPD I, a generally short-term, non-distressing, benign and reversible state accompanied by a pleasant affect. In contrast, the second HPPD Type we refer to as HPPD II, a generally long-term, distressing, pervasive, either slowly reversible or irreversible, non-benign state accompanied by an unpleasant affect. HPPD I and II appear to be part of a broad spectrum of non-psychopathological and psychopathological states reported by hallucinogen users. HPPD I and II may be clinically characterized by prodromal symptoms, onset, content of visual imagery, precipitators, frequency, duration and intensity of perceptual recurrences, severity, course, differential diagnosis, accompanying mood and affect, insight and remission. Pharmacological therapy with or without preceding or following co-occurring psychiatric disorders have been shown to ameliorate this syndrome. A large variety of medications may be utilized to alleviate this condition, but with differential results suggesting several subtypes. The purpose of this manuscript is to provide a clinical-oriented, comprehensive and concise review to treating psychiatrists.